Sensor devices for wear detection and/or for detecting the actuation stroke of disc brakes are known with different configurations.
For example, from EP 0 492 143 it is known to sense the wear of the brake linings at the end of an adjustment spindle of the actuation mechanism, which end faces away from the brake disc, in that the rotation of that adjustment spindle, which correlates with the translatorial movement of the brake pad for compensating the wear-induced clearance, is considered as a quantity. A similar method is also described in EP 0 566 006.
DE 43 12 377 discloses a sensor device in which the displacement movement of the brake actuation mechanism in the brake caliper is detected preferably by means of a linear potentiometer.
Moreover, from EP 0 784 162 a wear monitoring device is known in which the movement of a thrust spindle is detected by means of a gearing. For that purpose, the thrust spindle comprises a gear rack which meshes with a pinion of a sensor unit.
From WO 2004/111484 of the applicant it is known to sense the movement of the thrust spindle of the actuation mechanism at the face surface of the thrust spindle facing away from the brake disc in a linear manner.
For example, DE 42 30 831 discloses a sensor unit which is arranged in a separate housing, which housing is arranged at the rear side cover of the housing of the brake caliper of a disc brake. The detection mechanism received in the housing of the sensor unit is directly connected to the rear end of the thrust spindle thereby enabling torque transmission.
Similar mechanisms which sense the rotational movement of a spindle of an adjustment mechanism are e.g. known from WO 2007/140985 or from DE 10 2006 042 777, in which the rotation of the spindle is measured by the respective sensors in a touchless manner.
Plenty of configurations according to the prior art are realized in such a way that the adjustment mechanism of the clamping mechanism comprises a possibility of connecting the wear sensor and separate therefrom a further possibility for the temporary attachment of a tool by which the adjustment mechanism can be returned during a pad change.
These both connections are configured separate from each other since for cost reasons it would not be accepted by the market if for the purpose of pad change the sensor mechanism has to be removed, since such assembly steps could damage sealing elements for sealing the interior of the brake caliper to the outside, which sealing elements exist between the sensor housing and the brake caliper and an opening provided in it for the sensor housing, respectively, whereby new sealing elements have to be installed when subsequently the sensor mechanism has to be re-mounted. Moreover, the sensor has to be exactly mounted and aligned and, if needed, calibrated again upon reinstallation.
Moreover, depending on the configuration of the brake caliper on the one hand and on the configuration of the clamping mechanism with a corresponding adjustment unit on the other hand different design and in particular mechanical and kinematical adaptations become necessary in order to be able to install the sensor devices, which in turn results in additional costs. There exist disc brakes which are configured for a later installation of a corresponding sensor unit and there exist such for which this can be realized with disproportionate high efforts only. Beside these design adaptations also different sealing elements have to be always provided in order to avoid the intrusion of dirt and water into the interior via the openings provided in the housing of the brake caliper for the sensor units, whereby the clamping mechanism and the adjustment mechanism could substantially be harmed thereby reducing the functional safety.
Diverse mechanisms for the adaptation and other adaptors for sensor unit thus have to be kept on stock as spare parts with different configurations.